This invention relates to a sheet post-processing apparatus for selectively applying a process such as aligning or binding to sheets sent from an image forming apparatus such as a laser printer or copier, and also relates to an image forming apparatus equipped with this sheet post-processing apparatus.
Conventionally, as shown in FIG. 34 and FIG. 35, it is known that there is a sheet post-processing apparatus 201 mounted to an image forming apparatus such as a laser printer or a copier. The sheet post-processing apparatus is equipped with an intermediate tray 222 to support an upstream side of a sheet fed from an image forming apparatus 200 and discharged by tray discharge rollers 214 and 215, and a stack tray 225 established at downstream of the intermediate tray 222 and below with the level 221 (FIG. 36(b)) being vertically moveable in the Z direction. The Sheet once discharged in a state of straddling both trays as shown in FIG. 36(a) is aligned by forcibly transporting to an alignment reference using an abutting plate 217 and a position plate 223 by a discharge alignment belt 216 and a second alignment belt 302. While maintaining the sheet straddling both trays, a sheet bundle is formed by sequentially discharging the sheet as shown in FIG. 36(b). Then, after a post-processing of the sheet bundle such as stapling with the stapler 224, the sheet bundle is pressed by discharge means composed of the abutting plate 217 as shown in FIG. 36(c), and the apparatus discharges the sheet sequentially to the stacking tray 225 (Japanese Patent No. 08-9451). Note that a trailing edge of the sheet on the stack tray 225 is regulated by the level 221 relative to the intermediate tray 222 (a regulating plate 226).
However, the conventional sheet post-processing apparatus described above has the intermediate tray 222 first, then the stack tray 225 in the sheet transport direction, and is configured to perform the alignment and the stapling on the intermediate tray 222. Subsequently, the sheet bundle is removed and stacked downstream in the transport direction. Thus, since the intermediate tray 222 and the stack tray 225 are aligned sequentially in a plane, the dimensions of the apparatus becomes larger by a size of the intermediate tray 222 in addition to a length of the stack tray 225.
Also, even if the length of the intermediate tray 222 is shortened as much as possible in the transport direction, as a sheet for the next one cycle is received after post-processing for one cycle of the sheet to be stapled, it is necessary to have a space on the intermediate tray 222. Thus, the finished sheet bundle needs to be pushed downstream in the sheet transport direction. In other words, it is required to have a distance for offsetting the sheet bundle in the transport direction between an aligning position (an abutting plate 217) for stapling the sheet bundle and a position for regulating the trailing edge of the sheet (a level 221). Because a length equivalent to the distance is established as a length in the transport direction, a dimension of the sheet post-processing apparatus in the transport direction becomes longer. Also, it is necessary to transport the sheet bundle that is finished such as by stapling to a position on the stack tray 225 where the trailing edge of the sheet is regulated by the level 221, thereby causing a wasted time corresponding to an amount of time for the transport.
On the other hand, because the sheet tends to move to the stacking tray 225 due to the level 221 between the aforementioned intermediate tray 222 and the stacking tray 225 when stapling the sheet bundle, it is necessary to halt the movement of the sheet bundle and stabilize it to execute the stapling.
In the aforementioned conventional apparatus, it is tried to stop the sheet bundle on the stacking tray 225 through an engagement between a sheet surface including two downstream corners and a stacking surface of the stacking tray. However, in an actual case, the engagement of the sheet surface including the two downstream corners is not enough to fully prevent the sheet from moving, resulting in a problem that the sheet bundle is stapled while each sheet in the sheet bundle is shifted.
To handle this problem, a method is known in which the stacking tray 225 is elevated to eliminate the level 221 between the intermediate tray 222 and the stacking tray 225. However, in that case, it is necessary to add a mechanism for elevating and lowering the stacking tray 225. For that reason, the apparatus becomes larger and the cost increases. Further, because the stacking tray needs to be elevated and lowered in an appropriate range, a control becomes more complex, thereby causing a new problem.
Furthermore, this approach can not be applied to a compact apparatus with a fixed stacking tray, thus can not obtain a perfect solution for the problem.
An object of the present invention is to resolve the issues in the conventional technology, and to provide a compact sheet post-processing apparatus with a small size in the sheet transport direction and an image forming apparatus equipped with the aforementioned sheet post-processing apparatus. Further, an object is to provide a sheet post-processing apparatus and an image forming apparatus equipped with the sheet post-processing apparatus that can stabilize the sheet bundle to accurately execute the post-processing on the sheet bundle stacked straddling an intermediate tray and a stacking tray.
To attain the aforementioned objectives, the sheet post-processing (finishing) apparatus according to the present invention is provided with discharge means for discharging a sheet; sheet single corner portion support means for supporting one corner of the sheet discharged by the aforementioned discharge means; sheet storage means established under the aforementioned sheet single corner portion support means; and post-processing means for post-processing the sheet straddling the aforementioned sheet single corner portion support means and the aforementioned sheet storage means.
The sheet post-processing apparatus according to the present invention may be further provided with sheet moving means for moving the sheet finished by the aforementioned post-processing means and for discharging the sheet to the aforementioned storage means.
In the sheet post-processing apparatus according to the present invention, the aforementioned sheet storage means supports three corners of the sheet, excluding a corner portion of the sheet supported by the aforementioned sheet single corner portion support means, when the aforementioned post-processing means applies the post-processing.
The sheet post-processing apparatus according to the present invention may be further provided with drive means for driving the aforementioned sheet moving means between the aforementioned support means and the aforementioned storage means.
In the sheet post-processing apparatus according to the present invention, the aforementioned sheet single corner portion support means is formed so that an edge of an upper surface of the aforementioned sheet single corner portion support means supporting the sheet is completely positioned closer to a side of a single corner of the aforementioned sheet than a line drawn between two neighboring corners relative to the one corner of the aforementioned sheet when the aforementioned discharge means discharges the smallest size of the sheet to be handled.
The image forming apparatus according to the present invention is equipped with the aforementioned sheet post-processing apparatus.
As described above, the sheet post-processing apparatus or the image forming apparatus according to the present invention is provided with the discharge means for discharging the sheet; the sheet single corner portion support means for supporting one corner of the sheet discharged by the aforementioned discharge means; the sheet storage means established under the aforementioned sheet single corner portion support means; and the post-processing means for post-processing the sheet straddling the aforementioned sheet single corner portion support means and the aforementioned sheet storage means. More specifically, an intermediate tray, where the sheet is to be finished, needs to support just one corner of the sheet, as opposed to the conventional apparatus that supports two corners of the sheet. Therefore, the intermediate tray itself can be made compact, and the whole sheet post-processing apparatus can be made compact.
Also, the sheet storage means is established under the sheet single corner portion support means to support three corners of the sheet, thus the sheet is securely supported by the sheet storage means. Since the sheet is stable even in the state of straddling the sheet single corner portion support means and the sheet storage means, the post-processing means can apply the post-processing in a stable manner. Therefore, no shifting of the sheet will occur when the sheet bundle is stapled.